Mozart's penultimate piano sonata dates from 1789, a barren year for composition by his prolific standards, the only other major works produced being the final Piano Sonata in D major, K. 576, the first of the "Prussian" string quartets (in D major, K. 575), and the Clarinet Quintet in A major, K. 581. It was also the year of the composer's speculative journey to Berlin, Leipzig, and Dresden, a tour that failed to alleviate Mozart's by then desperate financial straits. Prior to setting off for Germany in the spring, he composed the B flat Sonata, entering it into his thematic catalog during February. His entry for it specifies the work as being a sonata auf Klavier allein (for piano alone), but curiously the sonata was long known in a version for violin and piano. This originated with the first published version, which appeared in Vienna in 1796 with a violin part so lacking in invention that it can be considered spurious with near certainty. It seems likely that, like its immediate predecessor, the so-called "facile" Sonata in C major, K. 545, the sonata was composed for didactic purposes. The opening Allegro is quite light in character; although on an altogether more modest scale than the sonatas composed earlier in the decade, it is masterful in the way it wrings various structural and contrapuntal implications from its deceptively bare opening. E flat Adagio is a rondo with two episodes that sets out to beguile rather than convey profundity. The final Allegretto bubbles with humor and surprise effects; it is one of the many finales in which Mozart evokes the world of opera buffa. Musicologist Alfred Einstein called the work "perhaps the most completely rounded of...all , the ideal of his piano sonata."